Automatic regulator control



J1me 1952 R. RUNALDUE AUTOMATIC REGULATOR CONTROL Filed Feb. 8, 1951 Inventor: Lew'i s Rfiun aldue,

His Attorney.

Patented June 17, 1952 AUTOMATIC REGULATOR CONTROL Lewis B. Runaldue, Dalton, Mass., assignor to General Electric Company, a corporation of New York Application February 8, 1951, Serial No. 209,947

Claims.

This invention relates to automatic regulator control and more particularly to an electronic fail safe time delay relay for reversible motor driven voltage regulators.

The trend in recent years on power circuits where voltage fluctuations occur rapidly and often has been toward the introduction of time delay between the operation of a conventional voltage regulating relay contact and the starting of a servomotor usually employed to drive an automatic voltage regulator. The objective has been to eliminate unnecessary corrections due to temporary voltage transients and thus increase the life of the regulator driving mechanism. Fulfillment of this objective has been practically mandatory in connection with step voltage regulators and load ratio control apparatus where the life of the contacts involved is definitely limited. To secure this time delay feature, various arrangements including those involving the use of mechanical timers have been employed in the past, but due to certain adverse and well-known experiences with mechanical timers, electronic time delay relays are now sometimes preferred.

Heretofore, however, electronic timers have had a serious drawback. For example, if an electronic tube failed because of loss of emission or gain, the conventional voltage regulating relay lost control of the regulator so that the regulator was rendered ineifective to thereafter automatically carry out its function of boosting or lowering the voltage pending replacement of the tube. On the other hand, the voltage regulator servo mechanisms are built sturdily and can withstand almost continuous running operation for long periods of time so that in the interest of continuity of service, it would be very desirable, in the event of tube failure, to automatically return sole control to the conventional voltage regulating relay, even though it would thereafter effect operation of the servomotor without time delay pending replacement of the defective tube. In other words, it would be desirable to have an arrangement exhibiting the time delay feature which would fail safe in the sense that the voltage regulating relay would thereafter control operation of the regulator rather than being rendered entirely ineffective because of the failure.

It is therefore an object of this invention to provide an improved electronic control device which will cause a selectable time delay between operation of a voltage regulating relay contact and operation of the servomotor of the induction voltage regulator.

It is also an object of this invention to provide an electronic device which will allow a voltage regulating relay to continue, but without time delay, to control the induction voltage regulator if the electronic tube fails due to loss of emission or gain.

It is a further object of this invention to provide a time delay control meetin these objectives which control can be initiated or operated by either the raise or lower contacts in the conventional voltage regulating relay, without employing two separate and identical time delay circuits or auxiliary relay means.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the single figure of the accompanying drawing, I have shown therein diagrammatically, by way of example, an embodiment of my invention for controlling an automatic voltage regulating system for a circuit Iii-l0. The numeral ll identifies an induction voltage regulator connected in the usual mannor to the circuit H! for regulating its voltage. Regulator II is of the conventional type having a movable coil therein driven through a shaft l2 by servomotor [3 which may be energized from main circuit through a pair of contacts 14 which, when bridged, will cause motor [3 to rotate the coil of regulator II in one direction to effect a lowering of the voltage, for example, of the circuit I0|U. Servomotor l3 may also be energized through a pair of contacts l5 which, when bridged, will cause motor 13 to rotate the regulator coil in the opposite direction to effect a boosting of the voltage of Iii-4 6. As illustrated, energization of servomotor I3 is controlled by a motor control relay comprising a lowering coil [6 energization of which causes bridging of contacts [4 and a boosting or raising coil l'l energization of which causes bridging of contacts [5. Also, as illustrated, coils l6 and I1 are in two independent control circuits having the contacts of a normally closed relay or switch l8 therein in series circuit relation with a control switch [9. Control switch 19 is a well-known and conventional contact-making voltmeter or voltage regulating relay and comprises a control coil 20 connected to respond to the voltage of circuit Iii-fi 0, a pivotally mounted contact arm or beam 2| and a pair of relatively fixed contacts 22 and 23 respectively connected to or mounted in the two independent control circuit-s. Arm 2| is shown in its normal operating position and it is adapted to be moved by coil into circuit controlling position wherein it makes contact with either relatively fixed contact 22 or relatively fixed contact 23. The voltage regulating relay also includes a holding efiect coil 24 energization of which is under the control of contact 22 or contact 23 through circuits which include fixed resistances 25, 20, 2?, 28 and a variable resistance 29 which allows adjustment of the amount of current through coil 24 and, therefore, the amount of holding efiect exercised by coil 24 to maintain steady contact between bridge arm 2| and contact 22 or 23, as the case may be. Relay l0 including holding coil 24 and the circuits associated therewith is a well-known device, sometimes referred to as a contact making voltmeter, and its operation is well understood by those skilled in the art. ment as thus far described, with the exception of normally closed relay or switch I8, is similar in many respects to a known arrangement for controlling the operation of a voltage regulator without time delay.

However, in accordance with this invention, relay or switch 8 with normally closed contacts in both of the independent control circuits is pro vided. The coil 30 of relay I8 is in series circuit relation with the anode-cathode circuit of an electronic discharge device 3| having an anode 32, a cathode 33, and a control grid 34. Energy for this circuit may be provided from main circuit |0| 0, as illustrated, through a transformer and series connected resistances 33 and 31, de-

fining a voltage divider, the common connection of which is connected to cathode 33. Another electronic discharge device 38 having an anode 39, a cathode 40, and a control grid 4| is also provided and may comprise a separate tube or be enclosed within the same envelope which encloses the elements of discharge device 3|, as i1- lustrated. In the interest of simplicity, the cathode heaters for tubes 3| and 38 have not been diagrammatically shown. These heaters may be energized from the illustrated secondary of transformer 35. It will hereinafter be understood by those skilled in the art that in lieu of heater type tubes, filament or cold cathode type tubes may be employed.

A cathode connected capacitor 42 is connected in the anode-cathode circuit of device 38 which may also be energized from main circuit |0-|0. The cathode of device 38 and one terminal of capacitor 42 are connected through a resistance 43 to the control grid 34 of electronic device 3|. The cathode and the same terminal of capacitor 42 are also connected to both of the independent control circuits for the coils |6 and ll of the motor control relay at points intermediate the normally closed switches |8 and the control switch l9, through an adjustable resistance 44 and respectively through fixed resistances 45 and 40 in series circuit relation with resistance 44, as illustrated. The control grid 4| of device 38 is connected to main circuit |0|0 through resistance 4i and resistances 48 and 49 comprising a voltage divider. In addition, it should be observed that the control grid is also connected to the two independent control circuits through one or more rectifiers or unidirectional conductive devices 50-50 nd 5|5| respectively. Although rectifiers 50-40, 5i5| may be of the copper oxide or selenium type, the germanium type rectifier is preferred inasmuch as copper and In fact, the entire arrangeselenium rectifiers will be permanently damaged if they break down due to excessive voltage, while germanium rectifiers are much more reliable in that the germanium diode will recover completely on removal of the voltage as long as the current resulting from the breakdown does not overheat the diode to cause a burnout. Furthermore, the germanium diode has a lower forward resistance compared to any other rectifier and leakage current in a reverse direction is less than would be the case with either the copper oxide or the selenium type rectifier. The importance of this characteristic will become apparent from a discussion of the operation of the invention to follow. However, with a typical or illustrative set of values for the various impedances employed, the type of tube or electronic discharge device, line voltage, etc. in mind, it is believed that this operation will be better understood. Thus, with a normal line voltage across the circuit |0-|0 of volts A. C., rectifiers 50-50 and 5|-5|' may each be, for example, a conventional and well known 1N63 germanium diode while electronic discharge devices 3|-38 may be a conventional 6SN7 twin triode tube. The various impedances illustrated may have approximate values in ohms resistance as follows: 500 ohms for each of the resistances identified by the numerals 2-5 and 26, 2280 ohms for resistance 21, 1800 ohms for 28, 750 ohms for 29, 10,000 ohms for 41, 40,000 ohms each for resistances 45 and 46, 15,000 ohms for 48, 20,000 ohms for 49, 5 megohms for 44, 20 inegohms for 43, 9,000 ohms for 36 and 2,500 ohms for resistance 31 while capacitor 42 may have a capacitance of 5 microfarads.

Under normal conditions, when the voltage level being maintained by the regulator II is within the band selected, arm 2| of relay I9 is maintained in the neutral or out-of-contact position illustrated and a positive potential with respect to cathode 40 is impressed upon the grid 4| of electronic discharge device 38 during the half-cycles when the upper line I0 is positive, so that device 38 is rendered conductive to maintain a charge on capacitor 42 approximately up to the peat: of the voltage existing at the junction between resistances 43 and 49. Although the control grid 4| is also connected to upper line It! through the germanium rectifiers and resistances 25, 27, 26 and 23, the resistances of the germanium rectifiers on the positive half cycle are very high relative to resistors 41, 48 and 49 so that the voltage peak to which capacitor 42 charges is determined by the voltage divider formed by resistors 48 and 49. Since electronic device 38 provides rectifying action, the negative peaks, of course, are unimportant. Under these conditions the charge on capacitor 42 at the terminal connected to cathode 40 is positive with respect to lower line or ground |0. Since the capacitor 42 is positive with respect to ground, the grid of electronic discharge device 3| is positive enough with respect to cathode 33 to cause current to flow in the plate or anode-cathode circuit thereof when the plate is positive so that coil 30 of relay I3 is energized whereby both of the normally closed switches in the independent control circuits are held in an open position. capacitor 52 is connected in shunt across relay coil 30 to smooth the current therethrough and prevent chattering. Although capacitor 42 is also connected to the upper A.-C. main l0 through resistors 44, 45, 2'! and 25 as well as through resistors 44, 4B, 28 and 20, it should also be pointed out that its reactance is low compared to the resistors involved so that the A.-C. ripple applied to the grid 34 of device 3| is low and can be neglected.

Now, assume the case where the voltage regulating relay l9 calls for an increased voltage from the induction voltage regulator by engagement of arm 2| with contact 22 in the control circuit completion of which would ordinarily energize boosting coil I! of the motor control relay. However, since the normally closed switch in this circuit controlled by relay I8 is held open as previously explained, coil I! will remain de-energized. Of course, because of the closure of control switch l9, current will flow through holding effect coil 24 through resistors 29, 26 and 21 in the proper direction with respect to the current in the solenoid coil 20 of the relay to give holding effect.

In addition, however, engagement of arm 2| with fixed contact 22 also initiates two other functions simultaneously. First, the grid of electronic discharge device 33 is connected to ground through germanium rectifiers 50 and 53 and the grid is virtually at ground potential on the positive half-cycles when the upper line It) is positive so that the device 38 discontinues maintenance of a charge on capacitor 42. On the negative half-cycles, of course, the resistance of rectifiers 50 and 50' is high but in addition device 38 will not charge the capacitor since the plate 39 of device 38 is negative. Secondly, and simultaneously, capacitor 42 starts discharging to ground through adjustable resistor 44 and fixed resistor 45. The time required to discharge capacitor 42 may be selected by adjusting resistor 44. Since the grid 34 of discharge device 31 would otherwise be positive enough to conduct current, resistance 43 has been placed in the circuit to limit this tendency. In relation to resistances 44 and 45 or 43, the resistance of resistor 43 is large. When the potential of capacitor 42 has been reduced, because of its discharge, to a certain predetermined value, the bias on the cathode 33 of device 3! furnished by the potential dividers 36 and 31 decreases the current in the relay coil 33 to a point where the normally closed switches controlled thereby drop to a closed position, as illustrated, whereupon the circuit controlling motor control relay coil IT is completed so that the resulting energization of coil I1 effects bridging of contacts l5-l5 to cause rotation of the servomo tor in the proper direction to raise the regulator voltage. Although the contacts associated with relay I8 in the circuit for energizing motor control relay coil I6 are also bridged simultaneously with the bridging of the contacts in the other control circuit. coil 13 remains substantially (ls-energized inasmuch as this circuit is broken or open at contact 23. The current in coil i3 is limited to an extremely small value relative to the amount required to operatively energize the relay, since the germanium rectifiers 5%50' are opposed in direction to the rectifiers 5l5i and the resist ances of resistors 45 and 43 are sufiiciently high in value.

If, instead of engaging contact 22, the arm 21 of voltage regulating relay 19 had engaged contact 23, coil It would, of course, have been energized after the selected time delay and the servomotor would have lowered the regulator voltage. In either case, after the regulator has restored line voltage to the proper level, the voltage regulating relay contact involved opens. The motor control relay coil involved is immediately deenergized so that the servomotor ceases to turn the regulator rotor. At the same time, the connections between capacitor 42 and ground is broken. The grid of device 38 returns to the potential as determined by the potential divider formed by resistors 48 and 43. Capacitor 42 recharges to a potential equal to the positive peak voltage existing at the grid plus a bias voltage required to cut device 38 off. The plate resistance of the electronic discharge device is low enough to consider the charging time of capacitor 42 to be instantaneous when compared to the time constants involved in the servo control circuit of an induction voltage regulator. Obviously, if a fixed rather than an adjustable time delay period is preferred, resistor 44 may be a fixed rather than an adjustable resistor.

In the event that either one or the other of the electronic discharge devices 3! and 38 should fail relay or switch 18 will be de-energized and its contacts will close. In such event, it will be apparent that the voltage control relay 19, the motor control relays involving coils I6 and I! and the voltage regulator l I will continue to adjust the line voltage, although the time-delay feature will be absent. I have thus provided a cooperative combination of elements so arranged that an adjustment of voltage by a voltage regulator will be delayed a predetermined period of time, but at the same time an arrangement has also been provided which is fail safe in the sense that failure of the elements employed to realize the time-delay feature will not interfere with continued automatic operation of the regulator without time delay.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications can be made therein and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within. the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a contactor mechanism operable for a movement between two separate stationary positions, and an operable control switch to control the operation of said contactor mechanism, a capacitor, a source of unidirectional potential, means responsive to an applied signal of a given polarity for charging said capacitor from said source, control means responsive to a given polarity charge on said capacitor for maintaining said contactor mechanism in one of said stationary positions, said control means being responsive to the discharge of said capacitor to a given level to cause movement of said contactor mechanism to the other of said stationary positions, a unidirectional conductive device operative in response to operation of said control switch to effect interruption of said applied signal and a resistance operative to effect discharge of said capacitor in response to operation of said control switch.

2. A fail safe time delay relay for separate electrical completion of either one of two independent control circuits, each having a normally closed switch therein and a control switch having contacts respectively connected in series circuit relation with said normally closed switches comprising means including an electronic discharge device having an anode, a cathode and a control grid effective when rendered conductive to simultaneously maintain said normally closed switches in the open position, means for impressing a positive potential on said control grid to render said discharge device conductive including a second electronic discharge device having an anode, a control grid and a cathode, said cathode connected to the grid of said first-mentioned discharge device, a pair of series connected resistances interconnecting said control circuits at points intermediate said control switch and said normally closed switches, means responsive a predetermined time after a closure of said control switch to render said first-mentioned discharge device non-conductive including oppositely poled unidirectional conductive devices respectively connected in parallel between the grid of said second discharge device and said control circuit at points intermediate said control switch and said normally closed switches and a resistance connected between the cathode of said second discharge device and the junction between said series connected resistances.

3. A motor control system comprising switch means for energizing a motor, two independent control circuits including a control switch movable to one closed position by engagement with a contact in one of said control circuits to control the operation of said switch means so as to cause operation of said motor in one direction and movable to another closed position by en gagement with a contact in the other of said con trol circuits to control the operation of said switch means so as to cause operation of said motor in the other direction, a normally closed switch in each of said control circuits respectively in series circuit relation with said control switch, timing means for simultaneously holding said normally closed switches open to render said control switch inefiective for a predetermined time after a closure thereof including a pair of electronic discharge devices each of which has an anode, a cathode and a control grid, a cathode connected capacitor in the anode-cathode circuit of one of said discharge devices, a coil for simultaneous actuation of said normally closed switches in the anode-cathode circuit of the other of said discharge devices, means for impressing a positive bias with respect to the cathode on the grid of said one discharge device to render said device conductive to charge said capacitor, the grid of said other discharge device being connected to the junction between the cathode of said one discharge device and said capacitor whereby said capacitor is efiective when charged to impress a positive potential on the grid of said other discharge device to render said device conductive and efiective to energize said coil to hold said normally closed switches open, said control circuits being interconnected at points between said control switch and said normally closed switches through series connected oppositely poled germanium rectifiers and separately interconnected at said points through a pair of series connected resistances, the grid of said one discharge device being connected to said control circuits respectively through said rectifiers and the cathode of said one device being connected through another resistance to an intermediate point between said series connected resistances whereby closure of said control switch eifects the impression of a negative potential with respect to the cathode on the control grid of said one discharge device to render said device inefiective to charge said capacitor and said capacitor is discharged through said other resistance to render the grid of said other discharge device negative with respect to 8 the cathode thereof whereby said coil in the anode-cathode circuit of said other device is deenergized and rendered ineffective to hold said normally closed switches open.

4. A fail safe time delay relay for separate electrical completion of either one of two independent control circuits comprising a contactor mechanism having contacts in each of said control circuits and operable for movement between two circuit controlling positions, an operable control switch to control the operation of said contactor mechanism, a capacitor, a source of unidirectional potential, means responsive to an applied signal of a given polarity for charging said capacitor from said source, control means responsive to a given polarity charge on said capacitor for maintaining said contactor mechanism in one of said circuitcontrolling positions, said control means being responsive to the discharge of said capacitor to a given level to cause movement of said contactor mechanism to the other of said circuit controlling positions, oppositely poled unidirectional conductive devices connected in series circuit relation between said control circuits, a pair of resistors connected in series circuit relation between said control circuits and a third resistor in series circuit relation respectively with each of said pair of resistors, said unidirectional conductive devices of a common polarity and said third resistor being operative in response to operation of said control switch to effect interruption of said applied signal and discharge of said capacitor.

5. A fail safe time delay relay for separate electrical completion of either one of two independent control circuits comprising a contactor mechanism having contacts in each of said control circuits and operable for movement between two circuit controlling positions, an operable control switch to control the operation of said contactor mechanism, a capacitor, a source of unidirectional potential, means responsive to an applied signal of a given polarity for charging said capacitor from said source, control means responsive to a given polarity charge on said capacitor for maintaining said contactor mechanism in one of said circuit controlling positions, said control means being responsive to the discharge of said capacitor to a given level to cause movement of said contactor mechanism to the other of said circuit controlling positions, unidirectional conductive devices connected to said control circuits operative in response to operation of said control switch to eilect interruption of said applied signal and a resistance connected to said control circuits simultaneously operative to effect discharge of said capacitor in response to operation of said control switch.

LEWIS R. RUNALDUE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,249,488 Nickle July 15, 1941 2,280,898 Dyer Apr. 28, 1942 2,342,821 Reagan Feb. 29, 1944 2,435,027 Blomberg Jan. 27, 1948 2,513,222 Wilson June 27, 1950 2,549,149 White Apr. 27, 1951 

